1. Field of the Invention
The invention relates to image sensing devices, and more particularly to a color filter structure having improved resolution and reduced cross-talk issues for an image sensing device.
2. Description of the Related Art
Image sensors are necessary components in many optoelectronic devices, including digital cameras, cellular phones, and toys. Conventional image sensors include both charge coupled device (CCD) image sensors and complementary metal oxide semiconductor (CMOS) image sensors. An image sensor typically includes a plane array of pixel cells, wherein each pixel cell comprises a photogate, photoconductor or a photodiode having a doped region for accumulating a photo-generated charge.
In addition, a periodic pattern of different colors is superimposed over the plane array of pixel cells. This periodic pattern of different colors is known as a color filter array (CFA). The periodic pattern of different colors is typically made of I-line photosensitive materials such as dye-type photosensitive materials or pigment-type photosensitive materials, such that formation of the periodic pattern of different colors is typically achieved by photolithography processes. The pigment-type photosensitive materials, however, show poor resolution performance in the photolithography processes when compared with the dye-type photosensitive materials. The dye-type photosensitive materials, however, show poor chemical duration in the photolithography processes when compared with the pigment-type photosensitive materials. Therefore, accurate definition of the periodic pattern in the color filter array, however, is problematic and becomes more critical as a size thereof is further reduced to, for example, a sub-micron size. Moreover, the resolution limitation of I-line photolithography tools for performing the photolithography processes to the I-line photosensitive materials of the color filter array is also limited as a size thereof is further reduced to, for example, a sub-micron size.